This application claims the benefit of Korean Patent Application No. 2002-34974, filed Jun. 21, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an office machine, such as a laser printer, photocopier, or the like, and more particularly, to driving apparatus and method in a double-side printable office machine which can reduce a waste toner amount and a volume of a developing unit, decrease wear and tear and noise of the developing unit, and prevent unnecessary driving of the developing unit during fixing, discharging and, in particular, returning a sheet of paper by driving, fixing, discharging, and returning operations for double-side printings separately from paper pickup/supply and developing operations.
2. Description of the Related Art
In general, as shown in FIG. 1, a double-side printable office machine, such as a double-side printing laser printer 1, includes a paper-supplying cassette 11 detachably mounted to a frame 10 of a main body of the double-side printable laser printer 1, a pickup/transport unit 6 picking up and transporting a sheet of paper P loaded in the paper-supplying cassette 11, a developing unit 30 forming a toner image on the sheet P, a fixing unit 40 heat-pressing the toner image formed on the sheet P to fix the toner image as a visible toner image, a paper discharge unit 50 discharging the sheet P on which the visible toner image is fixed by the fixing unit 40, and a double-side printing unit 80 re-feeding a one-side printed sheet P through the fixing unit 40 to the developing unit 30 to print the other side of the sheet P.
The paper-supplying cassette 11 is installed in a lower side of the frame 10 of the main body and supports the sheet P through a paper-pressing plate 13 supported by an elastic spring 12 so that the sheets P elastically ascend and descend.
Over the paper-supplying cassette 11 is installed the pickup/transport unit 6 sequentially picking up and transporting the sheets P loaded in the paper-supplying cassette 11 one by one. The pickup/transport unit 6 has a first paper sensor (not shown) sensing whether the sheets P are loaded in the paper-supplying cassette 11, a first pickup roller 7 picking up the sheets P loaded in the paper-supplying cassette 11, and a transport roller 23 and reverse roller 24 transporting the picked-up sheet P to the developing unit 30 along a paper transport guide 22 forming a paper transport path A.
In order to manually supply the sheet P, the pickup/transport unit 6 includes a manual paper-supplying cassette 27 mounted to protrude toward a front of the main body, a second paper sensor (not shown) sensing whether the sheet P is loaded in the manual paper-supplying cassette 27, and a second pickup roller 25 picking up the sheet P loaded in the manual paper-supplying cassette 27 and transporting the sheet P toward a register roller 28 and a back-up roller 29. As described above, the manual paper-supplying cassette 27, the second paper sensor, and the second pickup roller 25 constitute a manual feeder.
The developing unit 30 is detachably installed on the frame 10 of the main body, is disposed over the pickup/transport unit 6, and includes a photosensitive drum 32 forming an electrostatic latent image by a laser beam emitted from a laser scanning unit (LSU) 76 based on an image signal, a charging roller 49 charging the photosensitive drum 32, a developing roller 47 developing the electrostatic latent image formed on the photosensitive drum 32 with toner to form the toner image, a cleaning blade 48 cleaning a toner waste remaining on a surface of the photosensitive drum 32 after the toner image is transferred to the sheet P, and a waste toner bin 46 storing the toner waste.
Under the photosensitive drum 32 of the developing unit 30 is installed a transfer roller 66 transferring the toner image formed on the photosensitive drum 32 to the sheet P.
The fixing unit 40 pressing and fixing the toner image has a fixing roller 41 and a fixing backup roller 42.
The paper discharge unit 50 has first, second, and third paper discharge rollers 51, 55, and 60 and backup rollers 52, 63, 64, and 65 disposed along the paper transport guide 22 downstream in a paper transport direction of the fixing unit 40, and discharges the sheet P on which the toner image is fixed by the fixing unit 40, to an external paper discharge cassette 67.
The double-side printing unit 80 includes a paper reverse-transport guide 62 constituting a paper return path B for re-feeding a one-side printed sheet P to the developing unit 30 to print another toner image on a reverse side of the sheet P, a paper transport direction switching guide 54 directing a paper transportation so that the sheet P is transported to the paper return path B upon the double-side printing, and first and second reverse-transport rollers 70 and 90 transporting the sheet P through the paper transport path B.
The paper transport direction switching guide 54 is disposed at a position which the paper return path B comes across the paper transport path A, and is disposed upstream in the paper transport path A of the third paper discharge roller 60 of the discharge unit 50, thereby directing the sheet P to the paper return path B for the double-side printing.
In a double-side printing process of the laser printer 1 constructed as above, first, the sheet P loaded in the paper-supplying cassette 11 or in the manual paper-supplying cassette 27 is picked up by the corresponding first and second pickup rollers 7 and 25 based on an operation or a non-operation of the second paper sensor to automatically or manually feed the sheet P, and conveyed to the developing unit 30 through the register roller 28 along the paper transport guide 22.
While the sheet P is being conveyed to the developing unit 30, the electrostatic latent image is formed on the photosensitive drum 32 of the developing unit 30 by the laser beam emitted from the LSU 76 according to the image signal, and the toner is attracted to the electrostatic latent image developed on the photosensitive drum 32 by the developing roller 47 so that the electrostatic latent image is developed to the toner image in a visible form.
The toner image formed on the photosensitive drum 32 is transferred, when the sheet P is transported to the developing unit 30 along the paper transport guide 22, on one side of the sheet P, that is, on an upper side of the sheet P by the transfer roller 66, and the toner image transferred on the upper side of the sheet P is fixed on the upper side of the sheet P by the fixing roller 41 and the fixing backup roller 42 which constitute the fixing unit 40.
After the toner image is transferred on the upper side of the sheet P from the photosensitive drum 32, the toner waste remaining on the surface of the photosensitive drum 32 according to a transfer efficiency is removed by the cleaning blade 48 and stored in the waste toner bin 46 located below the cleaning blade 48.
The sheet P passing through the fixing roller 41 and the fixing backup roller 42 progresses into the third paper discharge roller 60 by the first and second paper discharge roller 51 and 55. At this time, the sheet P pushes a third paper sensor 44 located downstream in the paper transport direction of the fixing roller 41, and, accordingly, the third paper sensor 44 senses a passage of the sheet P.
At this time, when the printer 1, performs a one-side printing mode, the sheet P is discharged to the paper discharge cassette 67 through the third paper discharge roller 60.
However, when the printer 1 carries out a double-side printing mode, the third paper discharge roller 60 is driven to be reversely rotated by a controller as a certain period of time lapses after a rear end of the sheet P passes through the third paper sensor 44, that is, as the rear end of the sheet P reaches downstream in the paper transport direction of the switching guide 54 to be extended to the paper return path B using a stiffness of the sheet P itself. As a result, the sheet P is not externally discharged out of the printer 1, but progresses into the paper reverse-transport guide 62.
The sheet P transferred into the paper reverse-transport guide 62 is conveyed toward the second reverse-transport roller 90 by the first reverse-transport roller 70, and conveyed again to the developing unit 30 through the transport roller 23 and the register roller 28 along the paper transport guide 22 from the second reverse-transport roller 90, and the sheet P is discharged to the external paper discharge cassette 67 after the reverse side of the sheet P, that is, the lower side of the sheet P is printed as stated above.
However, as shown in FIG. 2, respective constituents of the conventional laser printer 1 as described above are constructed to be operated by a first driving part 15 driven by a first driving motor 15a and a second driving part 57 driven by the second driving motor 57a. 
That is, the first driving part 15 has a first pickup roller gear 20a, a transport roller gear 23a, a reverse roller gear 24a, a second pickup roller gear 25a, a register roller gear 28a, a photosensitive drum gear 32a, a fixing roller gear 41a, first and second paper discharge roller gears 51a and 55a, and first and second reverse-transport roller gears 70a and 90a which are respectively coupled to corresponding rollers to be associated in operation with the first driving motor 15a by plural mid-connection or idle gears 16, 17, 18, 19, 20, 21, 31, 33, 34, 35, 36, 37, 38, 43, 45, 53, and 61, thereby rotating in the paper transport and return directions the first pickup roller 7, the transport roller 23, the second pickup roller 25, the register roller 28, the photosensitive drum 32 of the developing unit 30, the fixing roller 41 of the fixing unit 40, the first and second paper discharge rollers 51 and 55 of the paper discharge unit 50, and the first and second reverse-transport rollers 70 and 90 of the double-side printing unit 80.
The second driving part 57 has a third paper discharge roller gear 60a connected to be associated with the second driving motor 57a through mid-connection gears 58 and 59 to forward or backward drive the third paper discharge roller 60 so that the sheet P passing through the first and second paper discharge rollers 51 and 55 is discharged through the third paper discharge roller 60 in the one-side printing mode or returned to the paper reverse-transport guide 62 in the double-side printing mode.
As stated above, in the conventional double-side printing laser printer 1, the first driving part 15 carries out the operations of all the constituents except for the third paper discharge roller 60, that is, the operations of sheet pickups/supplies, developments, fixings, discharges, and reverse transports in the double-side printing mode, so that the first driving part 15 does not remain stationary, but continues to be driven from the beginning to the end of printing together with the second driving part 57.
Accordingly, when the sheet P is developed, fixed, and discharged, particularly, when the sheet P is returned to the paper reverse-transport path B in the double-side printing mode, the photosensitive drum 32 of the developing unit 30 is unnecessarily rotated with no load, and, accordingly, constituents of the photosensitive drum 32 of the developing unit 30 are worn and torn as well as generate noise, thereby reducing a lifespan and reliability of the printer 1.
Further, when the photosensitive drum 32 is rotated with no load, the toner attached to the surface of the developing roller 47 is attracted to and rotated with the photosensitive drum 32 by composite forces, such as potential differences on the surface of the photosensitive drum 32, and eventually collected into the waste toner bin 46 by the cleaning blade 48 as the waste toner.
As described above, as the photosensitive drum 32 is unnecessarily rotated for a long time, an amount of the toner used increases, and, accordingly, problems are brought out in that it is required to increase a volume of the waste toner bin 46 and the amount of the toner in designing the printer 1 so that a manufacture cost increases, and sizes of devices, such as the developing unit or the like, increase.
Further, in the conventional double-side printing laser printer 1, the developing unit 30 and the fixing unit 40 should be disposed close to each other in order to drive the developing unit 30 and the fixing unit 40 by one motor, that is, the first driving motor 15a, so that the waste toner can be fused on the photosensitive drum 32 of the developing unit 30, the cleaning blade 48, and the waste toner bin 46 by heat for fixing, and thereby a fatal problem, such as disablements or breakdowns of the corresponding constituents of the printer 1, can occur.
The present invention has been devised to solve the above and/or other problems, so it is an aspect of the present invention to provide driving apparatus and method in a double-side printable office machine which can not only reduce a size and a waste toner amount of a developing unit to decrease a manufacturing cost, but also reduce wear and tear and noise of the developing unit to enhance a lifespan and reliability of products by controlling paper pickup/supply and developing operations separately from an operation of fixing, discharging, and returning sheets for double-side printings.
It is another aspect of the present invention to provide driving apparatus and method in a double-side printable office machine which can prevent damage on a developing unit due to fixing heat of a fixing unit by separately controlling a developing operation and a fixing operation so that the fixing unit and the developing unit are disposed to be spaced-apart from each other by more than a certain range.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
In order to achieve the above and/or other aspects of the present invention, a driving apparatus for a double-side printable office machine includes a main body, a paper-supplying unit detachably mounted in a frame of the main body, a pickup/transport unit picking up and conveying a sheet of paper loaded in the paper-supplying unit in a paper transport direction, a developing unit forming a toner image on the sheet, a fixing unit heat-pressing the toner image formed on the sheet and fixing the toner image on the sheet as a visible image, a double-side printing unit having a paper return path through which the sheet having one side printed enters the developing unit to form another image on a reverse side of the sheet, and a transport part conveying the sheet through the paper return path, and a paper discharge unit discharging the sheet on which the visible image is fixed through the fixing unit.
The driving apparatus further includes a first driving part having a first driving motor and a first power transfer part transferring a power of the first driving motor to the pickup/transport unit, the developing unit, and a first roller of the transport part of the double-side printing unit to drive the pickup/transport unit, the developing unit, and the first roller of the transport part of the double-side printing unit, a second driving part having a second driving motor and a second power transfer part transferring a power of the second driving motor to the fixing unit, a second roller of the transport part of the double-side printing unit, and the paper discharge unit to drive the fixing unit, the second roller of the transport part of the double-side printing unit, and the paper discharge unit; and a controller controlling the first and second driving parts.
According to another aspect of the present invention, the first power transfer part of the first driving part includes at least one pickup roller gear connected to the first driving motor through at least one mid-connection gear, respectively, to drive at least one pickup roller, a photosensitive drum driving gear connected to the first driving motor through plural mid-connection gears to drive a photosensitive drum, and at least one first reverse-transport roller gear connected to the first driving motor through the plural mid-connection gears to drive the first roller of reverse-transport rollers of the transport part.
The second power transfer part of the second driving part includes a power transfer/cutoff part cutting off the power of the second driving motor to a fixing roller of the fixing unit and one of paper discharge rollers of the paper discharge unit when the second driving motor is driven in a direction for the sheet to re-enter the paper return path, and transferring the power of the second driving motor when the second driving motor is driven in a direction for the sheet to be discharged, a paper discharge roller gear connected to the second driving motor through the plural mid-connection gears to drive another one of the paper discharge rollers of the paper discharge unit in forward/reverse directions so that the sheet can be discharged or re-entered into the paper return path, and at least one second reverse-transport roller gear connected to the second driving motor through the plural mid-connection gears to drive the second roller of the reverse-transport rollers of the transport part.
The power transfer/cutoff part includes a latch gear disposed to be connected between the second driving motor, the paper discharge roller gear connected to the one of the paper discharge rollers, and the fixing roller gear.
The controller, in a double-side printing mode, controls the first driving motor of the first driving part to stop driving as a rear end of the sheet passes through the developing unit and reaches a certain position of the paper transport path and controls the first driving motor to be driven in the paper transport direction again when the sheet enters the paper return path and reaches a certain position of the paper return path. At this time, the controller obtains information on a stop position and a driving start position of the first driving motor by counting a period of time in which a movement of the sheet is detected by a register sensor disposed upstream in the paper transport direction of the developing unit and a paper sensor disposed downstream in the paper transport direction of the fixing unit.
Further, a position at which the first driving motor starts to drive, is set so that a first period of time needed for a process initialization of the developing unit is shorter than a second period of time during which a front end of the sheet in a paper progress direction on the paper return path moves to the developing unit after the start of the driving of the first driving motor.
Further, the controller, in the double-side printing mode, controls the first driving motor to completely stop when the rear end of the sheet exits the developing unit when the sheet is a last printing sheet.
Further, the second driving motor is, in the double-side printing mode, controlled to be forward rotated after stopping for a certain period of time or immediately after the sheet exits the second roller of the transport part driven by the second driving motor after entering the paper return path.
According to another aspect of the present invention, a driving method for a double-side printable office machine includes a main body, a paper-supplying unit detachably mounted in the frame of the main body, a pickup/transport unit picking up and conveying sheets of paper loaded in the paper-supplying unit, a developing unit forming a toner image on a sheet, a fixing unit heat-pressing the toner image formed on the sheet and fixing the toner image as a visible image, a double-side printing unit having a paper return path through which the sheet having one side printed enters the developing unit to form another image on a reverse side of the sheet, and having a transport part conveying the sheet through the paper return path, a paper discharge unit discharging the sheet on which the visible image is fixed, through the fixing unit, a first driving part having a first driving motor and a first power transfer part transferring power of the first driving motor to the pickup/transport unit, the developing unit, and a first roller of the transport part of the double-side printing unit to drive the pickup/transport unit, the developing unit, and the first roller of the transport part of the double-side printing unit, a second driving part having a second driving motor and a second power transfer part transferring power of the second driving motor to the fixing unit, a second roller of the transport part of the double-side printing unit, and the paper discharge unit to drive the fixing unit, the second roller of the transport part of the double-side printing unit, and the paper discharge unit, and a controller controlling the first and second driving parts.
The driving method further includes determining whether a mode is a double-side printing mode, stopping the first driving motor of the first driving part when a rear end of the sheet passes through the developing unit and reaches a certain position of a paper transport path in the double-side printing mode, driving the second driving motor of the second driving part in a direction conveying the sheet into a paper return path in the double-side printing mode, and driving the second driving motor in a direction discharging the sheet upon determining that the mode is not the double-side printing mode, when the rear end of the sheet swings in a direction of the paper return path, cutting off power transferred to one of paper discharge rollers of the paper discharge unit and the fixing unit from the second driving motor when the second driving motor is driven in a direction for the sheet to enter the paper return part, and driving the first driving motor of the first driving part in the paper transport direction again as the sheet enters the paper return path and reaches a certain position of the paper return path.
According to another aspect of the present invention, the stopping of the first driving motor includes obtaining information on a stop position of the first driving motor by counting a period of time in which a movement of the sheet is detected by a register sensor disposed upstream in the paper transport direction of the developing unit.
The driving of the first driving motor again includes obtaining information on a driving start position of the first driving motor by counting a period of time during which the movement of the sheet is detected by a paper sensor disposed downstream in the paper transport direction of the fixing unit.
According to another aspect of the present invention, the driving method includes setting a position at which the first driving motor starts driving so that a first period of time needed for a process initialization of the developing unit is shorter than a second period of time during which the front end of the sheet in the paper progress direction on the paper return path moves to the developing unit after starting the driving of the first driving motor.
The method further includes completely stopping the first driving motor when the rear end of the sheet exits the developing unit when the sheet is a last printing sheet.
Further, the method further includes driving the second driving motor in a direction for the sheet to be discharged after a stop for a certain period of time as the sheet is out of the second roller of the transport part driven by the second driving motor after the sheet enters the paper return path in the double-side printing mode. Alternatively, the method further includes driving the second driving motor in a direction discharging the sheet immediately when the sheet exits the second roller of the transport part driven by the second driving motor after the sheet enters the paper return path upon the double-side printing mode.
According to yet another aspect of the present invention, a driving method for a double-side printable office machine includes a paper-loading unit detachably mounted in the frame of a main body, a pickup/transport unit picking up and conveying sheets of paper loaded in the paper-loading unit in a paper transport path, a developing unit forming a toner image on a sheet, a fixing unit heat-pressing the toner image formed on a sheet and fixing the toner image as a visible image, a double-side printing unit having a paper return path through which the sheet having one side printed enters to the developing unit to form another image on a reverse side of the sheet, and having a transport part conveying the sheet through the paper return path, a paper discharge unit discharging the sheet on which the visible image is fixed through the fixing unit, a first driving part having a first driving motor and a first power transfer part transferring a power of the first driving motor to the pickup/transport unit, the developing unit, fixing unit, one of paper discharge rollers of the paper discharge-unit, and the transport part of the double-side printing unit to drive a first driving motor, the pickup/transport unit, the developing unit, the fixing unit, the portion of the paper discharge unit, and the transport part of the double-side printing unit, a second driving part having a second driving motor and a second power transfer part transferring a power of the second driving motor to another one of the paper discharge rollers of the paper discharge unit to drive the another one of the paper discharge rollers of the paper discharge unit, and a controller controlling the first and second driving parts.
The driving method further includes determining whether a mode is a double-side printing mode, stopping the first driving motor of the first driving part when a rear end of the sheet passes through the developing unit and reaches a certain position of the paper transport path when the mode is the double-side printing mode, driving the second driving motor of the second driving part in a direction conveying the sheet into the paper return path upon the double-side printing mode, and driving the second driving motor in a direction discharging the sheet upon determining that the mode is not the double-side printing mode, when the rear end of the sheet swings in a direction of the paper return path, and driving, upon determining that the mode is the double-side printing mode, the first driving motor of the first driving part in the paper transport direction again as the sheet enters the paper return path and reaches a certain position of the paper return path.
According to another aspect of the present invention, the stopping of the first driving motor includes obtaining information on a stop position of the first driving motor by counting a period of time in which a movement of the sheet is detected by a paper sensor disposed downstream in the paper transport direction of the fixing unit.
The driving of the first driving motor again includes obtaining information on a driving start position of the first driving motor by counting a period of time during which the movement of the sheet is detected by a paper sensor disposed downstream in the paper transport direction of the fixing unit.
Further, the driving of the first driving motor in the paper transport direction again includes setting a position at which the first driving motor starts driving, so that a first period of time needed for a process initialization of the developing unit is shorter than a second period of time during which a front end of the sheet in a paper progress direction on the paper return path moves to the developing unit after starting the driving of the first driving motor.
The method further includes completely stopping the first driving motor when a certain period of time lapses after a rear end of the sheet exits the fixing unit when the sheet is a last printing sheet.
Further, the method further includes driving the second driving motor in a direction for the sheet to be discharged after a stop for a certain period of time as the sheet is out of the another one of the paper discharge rollers of the paper discharge unit driven by the second driving motor after the sheet enters the paper return path in the double-side printing mode. Alternatively, the method further includes driving the second driving motor in a direction discharging the sheet immediately as the sheet is out of the another one of the paper discharge rollers of the paper discharge unit driven by the second driving motor after the sheet enters the paper return path in the double-side printing mode.